How do the last two stanzas of the darkling thrush function within the rest of the poem

Read the excerpt from "the love song of j. alfred prufrock." and indeed there will be time to wonder, “do i dare? ” and, “do i dare? ” time to turn back and descend the stair, with a bald spot in the middle of my hair— [they will say: “how his hair is growing thin! ”] my morning coat, my collar mounting firmly to the chin, my necktie rich and modest, but asserted by a simple pin— [they will say: “but how his arms and legs are thin! ”] do i dare disturb the universe? in a minute there is time for decisions and revisions which a minute will reverse. which lines indicate that the speaker is concerned about what others think of him?